COPERNICUS AND THE NEW ERA
Throughout the Middle Ages the progress of astronomy was held back by a
combination of untoward circumstances. A prolonged reaction from the
heights attained by the Greek philosophers was to be expected. The
uprising of the Mohammedan world, and the savage conquerors in the East
did not produce conditions favorable to the origin and development of
great ideas.
At the birth of Copernicus, however, in 1473, the time was ripening for
fundamental changes from the ancient system, the error of which had
helped to hold back the development of the science for centuries. The
fifteenth century was most fruitful in a general quickening of
intelligence, the invention of printing had much to do with this, as it
spread a knowledge of the Greek writers, and led to conflict of
authorities. Even Aristotle and Ptolemy were not entirely in harmony,
yet each was held inviolate. It was the age of the Reformation, too, and
near the end of the century the discovery of America exerted a powerful
stimulus in the advance of thought.
Copernicus searched the works of the ancient writers and philosophers,
and embodied in this new order such of their ideas as commended
themselves in the elaboration of his own system.
Pythagoras alone and his philosophy looked in the true direction. Many
believe that he taught that the sun, not the earth, is at the center of
our solar system; but his views were mingled with the speculative
philosophy of the Greeks, and none of his writings, barring a few meager
fragments, have come down to our modern age.
To many philosophers, through all these long centuries, the true theory
of the celestial motions must have been obvious, but their views were
not formulated, nor have they been preserved in writing. So the fact
remains that Copernicus alone first proved the truth of the system which
is recognized to-day. This he did in his great treatise entitled "De
Revolutionibus Orbium Coelestium," the first printed copy of which was
dramatically delivered to him on his deathbed, in May, 1543. The seventy
years of his life were largely devoted to the preparation of this work,
which necessitated many observations as well as intricate calculations
based upon them. Being a canon in the church, he naturally hesitated
about publishing his revolutionary views, his friend Rheticus first
doing this for him in outline in 1540.
So simple are the great principles that they may be embodied in very few
words; what appears to us as the daily revolution of the heavens is not
a real motion, but only an apparent one; that is, the heavens are at
rest, while the earth itself is in motion, turning round an axis which
passes through its center. And the second proposition is that the earth
is simply one of the six known planets; and they all revolve round the
sun as the true center. The solar system, therefore, is "heliocentric,"
or sun-centered, not "geocentric" or earth-centered, as taught by the
Ptolemaic theory.
Copernicus demonstrates clearly how his system explains the retrograde
motion of the planets and their stationary points, no matter whether
they are within the orbit of the earth, as Mercury and Venus, or outside
of it, as Mars, Jupiter, and Saturn. His system provides also the means
of ascertaining with accuracy the proportions of the solar system, or
the relative distances of the planets from the sun and from each other.
In this respect also his system possessed a vast advantage over that of
Ptolemy, and the planetary distances which Copernicus computed are very
close approximations to the measures of the present day.
Reinhold revised the calculations of Copernicus and prepared the "Tabulae
Prutenicae," based on the "De Revolutionibus," which proved far superior
to the Alfonsine Tables, and were only supplanted by the Rudolphine
Tables of Kepler. On the whole we may regard the lifework of Copernicus
as fundamentally the most significant in the history and progress of
astronomy.